An "annular eclipse" is being viewed from a 240 to 300km-wide swathe of Earth stretching from Asia across the Pacific to the western US.

The eclipse is happening at a time that the Moon is at its farthest from the Earth, and therefore does not block out the Sun completely.

Thousands of people across Asia have been witnessing the resulting "ring of fire".

From most parts of the path, it will last about four-and-a-half minutes.

The eclipse traced a path over Japan, almost directly over Tokyo, before crossing the Pacific. It passed just below Alaska's Aleutian islands and made landfall over the Oregon/California border in the United States.

In Japan "eclipse tours" were held at schools and parks, on pleasure boats and even private airplanes. Similar events were also held in China and Taiwan.

TV in Tokyo broadcast the event live.

Light rain fell on Tokyo as the eclipse began, but the clouds thinned as it reached its peak, providing near perfect conditions, Kazinform cites BBC News.

"It was a very mysterious sight - I've never seen anything like it," said Kaori Sasaki, who joined a crowd in central Tokyo.

Japanese electronics giant Panasonic sent an expedition to the top of Mount Fuji to film the eclipse using solar-powered equipment.

"Our goal is to broadcast the world's most beautiful annular eclipse from the highest mountain in Japan," the company said.

However, in Hong Kong skywatchers were not so lucky. Hundreds had gathered along the Kowloon waterfront where the Space Museum had set up solar-filtered telescopes, but heavy clouds obstructed the view.

The 3.5-hour event will become less visible as it reaches Texas on Sunday evening local time.

It is possible to see partial views of the eclipse across much of east Asia and North America.

The Slooh series of space telescopes has been covering the event on its website.